Rates of low back pain in the developing world have surpassed those of the developed world, with its prevalence growing in urban populations. A cross-sectional population-based study of 22,952 participants residing in Tehran, Iran, published in Spine, has found a one-year prevalence rate of 42.1%, at an estimated annual cost of US$7.1 million for the city.

Seeking to estimate the burden of low back pain on the city, and its biological and physical correlates, researchers used a four-stage sampling method to obtain a representative sample of the population. Using the 22 districts of Tehran as strata, 120 blocks were chosen at random from each stratum. In each block, eight households were selected at random, before participants themselves were chosen according to age and gender.

In “one of the largest urban population surveys in back pain epidemiology and its potential associated factors…conducted to date”, participants were initially surveyed by the “Urban HEART questionnaire – Tehran Model” to garner basic information such as age, sex and occupation. Quality of life was assessed by Iranian General Health Questionnaire (GHQ-28), which screens for psychiatric disorders. The researchers collected physical activity data by use of an Iran-specific Global Physical Activity Questionnaire (GPAC), developed by the World Health Organisation.

In addition to one-year prevalence results, the researchers found that 36.2% of participants were experiencing low back pain at the time of the survey, while 12.2% reported chronic low back pain. The authors write that these results are higher than both global and national Iranian mean low back pain prevalence values reported in literature. Sick leave due to low back pain was reported by 1.73% of participants in this study, with a mean of 24.12 days lost for these subjects. The mean work days lost due to illness was 0.41 in the overall study population.

A logistical regression analysis was determined which variables were most associated with low back pain. The researchers discovered that participants who had never been married were significantly less likely to report low back pain, with those currently married 1.5 times as likely to report current pain, when adjusted for other variables. Housewives were significantly more likely to report low back pain, which the authors speculate may be due to the repetitive nature of housework, often requiring bending and torsional movements. Women were significantly more likely to report low back pain, as were those with a higher body mass index, and those with lower levels of education.

Participants who scored more than six in the GHQ-28 questionnaire were roughly twice as likely to report low back pain, independent of other factors. Achieving more than six points was taken by the authors as an indication of psychological disorder, in keeping with the literature. Given that major depressive disorders are the second highest cause of disability in Iran, the authors suggest that “devising preventative and management strategies for these factors could play an effective role in preventing chronic lower back pain”, as well as addressing overall disability levels.

Whilst physical activity was associated with both acute and chronic low back pain, no significant associations could be drawn when tested as an independent variable. This analysis may be confounded by factors such as body mass index, suggest the authors.

The researchers report that this study is limited mainly by its reliance on participant self-reporting, leaving data open to participant recall bias and lapses in memory. The authors advise that the direct assessment of the severity of low back pain should be investigated in future research.

The authors conclude that low back pain could result in “a significant economy impact for many subjects, families and health care systems” in Tehran. Given the aging population of the city, the economic burden of low back pain is likely to rise. The authors suggest that, “educational programs, appropriate rehabilitation protocols, and preparation of a national guideline for low back pain management” might help to combat this challenge, which may be indicative of low back pain as “a subtle threat to urban populations in developing countries.”